Dear Kevin
As I expect you realise by now Crewkerne was a waste of time. It wasn't Percy in the register. It was so disappointing. there really is nothing more to be done. I have gone well over time as it is, as another idea surfaces.
These are my thoughts - not certainties.
You are not descended from the Percy who 'came from the north'. they consistently spell their name with an 'e' whereas your ancestors used the 'u' until fairly recent.
You are descended from the famous Percy family but from ones who moved down to Somerset much earlier and had been long established there and who had gone down in the world, but were coming up again!
Probably your ancestor was William of Bradford and the John we cannot find was the son of Christopher who left Bradford and moved to Bishops Hull. (Enclosed are P.C.s of relevant people. I can't prove that these are Purseys but the surname of Roger who we know was a Pursey appears with very strange spelling. We have to remember that these names were copied into the registers from notes which were often badly written and spelled. The name Gabriel is not common in this family but I have found one other in Chard.)
March 5
Another theory bites the dust. The name I wanted to be Percy actually looked more like Patchy. I looked this up in Taunton and found a Patche. However I still think the line descends through Christopher of Bishops Hull. Hundreds of baptisms etc. were lost because of the Civil war, the Purseys among them.
Enclosed an extract from The Daily Telegraph - any resemblance?
I'm really sorry I haven't been of more help. If I ever come across anything new I will let you know. I've searched everything in the RO but from time to time new stuff does come in. Did you get in touch with the Mormons?
Your sincerely